Monsoons are an important chapter in Geography for the UPSC exam. It is a part of the climate section and is very important since the Indian climate is dominated by this phenomenon. It is also significant for the country’s economy since a large part of Indian agriculture is dependent on monsoons. Hence, the importance of the monsoons for the IAS exam cannot be undermined.

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Monsoons Introduction

The word ‘monsoon’ is believed to have originated from the Arabic word for season ‘mawsim’. Monsoons are basically seasonal winds that reverse their direction according to the change in season. They are hence, periodic winds. The monsoons travel from the sea to the land in summers and from land to the sea during winters, hence, are a double system of seasonal winds. Historically the monsoons have been very important because these winds were used by traders and seafarers to move from place to place. Though there is monsoon in the Indian subcontinent, central-western Africa, Southeast Asia and a few other places, the winds are most pronounced in the Indian subcontinent.

India gets southwest monsoon winds in the summers and northeast monsoons during the winters. The former arise because of the formation of an intense low-pressure system over the Tibetan Plateau. The latter arises due to the high-pressure cells that are formed over the Siberian and Tibetan plateaus.

Southwest Monsoon:

Cause: Intense low-pressure formation over the Tibetan Plateau because of intense heating during the summer season; permanent high-pressure cell in the South of the Indian Ocean (East to Northeast of Madagascar in summer).

SW monsoon winds bring heavy rainfall to most parts of the country.

Factors influencing the onset of SW monsoons:

  1. Intense low-pressure formation over the Tibetan Plateau
  2. The permanent high-pressure cell in the South of the Indian Ocean
  3. Subtropical jet stream
  4. African Easterly jet (Tropical easterly jet)
  5. Inter-Tropical Convergence Zone (ITCZ)

Factors influencing intensity of SW monsoons:

  1. Strengths of the low pressure over Tibetan plateau and the high pressure over the south Indian Ocean
  2. Somali Jet
  3. Somali Current
  4. Indian Ocean dipole
  5. Indian Ocean branch of the Walker Cell

What are the two branches of Southwest Monsoon?

The southwest monsoon arrives in two branches called the Bay of Bengal branch and the Arabian Sea branch. The Arabian Sea side monsoon creates a low-pressure area on the Thar Desert. It is quite stronger than the Bay of Bengal side monsoon.

Which Indian state is the first to receive the Southwest Monsoon rains?

The Arabian Sea Branch of the Southwest Monsoon first hits the Western Ghats of the coastal state of Kerala, India, thus making this area the first state in India to receive rain from the Southwest Monsoon.

Why does the Southwest monsoon break into two branches?

South West monsoon winds break into two branches due to topographic factors. When the South West Monsoon wind hits the Western Ghats it branches into two parts, the Arabian Sea branch and the Bay of Bengal Branch.

Why does the Tamil Nadu coast remain dry during Southwest Monsoon?

During the South-West Monsoon, Tamil Nadu remains dry because it is located in a rain shadow area. Tamil Nadu has rain during the monsoon season due to the southwest trade winds which blow towards the northern hemisphere. Tamil Nadu receives rainfall in the winter season due to northeast trade winds.

Why does the Southwest Monsoon bring heavy rains?

Summer Monsoon weather is characterized by a strong, generally West or southwest breeze that is responsible for bringing significant rainfall to the Asian subcontinent and to South and East Asia. The significant southwest monsoon rainfall is a by-product of air passing over large areas of warm equatorial ocean, stimulating increased levels of evaporation from the ocean’s surface; the southwest monsoon air, now laden with water vapour, cools as it moves north and as it rises over land; at some point the air is no longer able retain its moisture and precipitates copious volumes to irrigate rice fields and drench rainforests, sometimes causing severe flooding.

Northeast Monsoon:

Cause: High-pressure cells over the Tibetan and the Siberian Plateaus

NE monsoon winds bring rainfall to the southeast coast of the country (Tamil Nadu coast and Seemandhra’s south coast).

Factors responsible for the formation of the NE Monsoons:

  1. Formation and strengths of the high-pressure cells over the Tibetan and the Siberian Plateaus during winters
  2. Migration of the Inter-Tropical Convergence Zone (ITCZ) to the south of India
  3. The high-pressure cells in the southern Indian Ocean migrating to the west and weakening

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